unix.utilities: remove platforms.txt since its portable
unix.utilities: remove platforms.txt since its portable

kingcons/factor,kingcons/factor,mcandre/factor,erg/factor,littledan/Factor,erg/factor,mcandre/factor,erg/factor,mcandre/factor,littledan/Factor,ceninan/factor,cataska/factor,erg/factor,mcandre/factor,mcandre/factor,cataska/factor,kingcons/factor,littledan/Factor,littledan/Factor,erg/factor,ceninan/factor,erg/factor,mcandre/factor,kingcons/factor,cataska/factor,erg/factor,ceninan/factor,ceninan/factor,mcandre/factor,cataska/factor